DESCRIPTION: The increased risk of endometrial cancer associated with the use of postmenopausal estrogen therapy can be diminished by the concomitant use of progestogen on a cyclic basis. Nevertheless, it is quite uncertain whether the entirety of the increased risk is eliminated, especially in long-term users of cyclic estrogen/progestogen regimens. Additionally, the impact on endometrial cancer incidence of a now-common way of taking hormones, on a combined-continuous basis, has never been evaluated. To address these questions, a population-based case-control study of endometrial cancer is proposed for women 50-60 years of age who reside in three counties of western Washington. An attempt will be made to interview eligible cases diagnosed during 1997-1999 regarding the use of hormonal medications and other exposures and characteristics that bear on the incidence of endometrial cancer. As a basis of comparison for the cases who are 50-64 years of age, interviews will be sough with 50-64 year-old female residents of these counties identified through random digit dialing. Controls 65-69 years of age will be identified through the records of the Health Care Financing Administration, and they will be interviewed as well. Potential controls who have previously had a hysterectomy will be excluded. We anticipate obtaining interviews with approximately 300 cases and an equal number of controls. Exogenous hormones offer postmenopausal women substantial benefits with regard to their cardiovascular and skeletal systems. The proposed study has the potential to obtain information that can guide their choice of hormonal regimen so as to minimize the likelihood of endometrial cancer as an adverse effect of this otherwise useful therapy.